Agrochemical formulations are generally designed based on customer needs and the physiochemical properties of the active ingredients, for example, the solubility of the active ingredient in water or non-aqueous solvents. There are two major categories of formulations, solid formulations and liquid formulations.
Granule products containing agricultural active ingredients represent one class of solid formulations that are seeing increased use today because of their relative safety compared to liquid formulations and the advantages they offer with regard to cost savings in packaging and transportation. Granule products, in the form of emulsifiable granules (EG), water dispersible granules (DG) and granules (GR) for broadcast application, may be used for insect, weed, fungal pathogen and nematode control and are often used in soil and aquatic environments. Because of the particle weight, granules used in aerial applications may pose a reduced hazard from off-target drift compared to aerial liquid spray applications.
Powder or wettable powder (WP) products containing agricultural active ingredients represent additional classes of solid formulations that are also used in agriculture and differ from granules primarily by their smaller particle size. Granules typically have a size range between about 200 to about 4000 micrometers (Wikipedia: Granulation—making of granules) and are much larger than the particles in powder formulations and therefore present less of a respiratory hazard. Granule products may be produced from powders or wettable powders in a granulation or agglomeration process.
Active ingredients, in the form of solids or liquids, may be formulated as granules and include insecticides, herbicides, fungicides, nematicides and plant growth regulators. Granule formulations usually contain a relatively small amount of the active ingredient since the granules are frequently not further diluted with a carrier solvent such as water prior to use, but are instead applied directly to the area of interest, such as for example, soil or water. Once applied, the active ingredient contained in the granule is released to the area of application, typically upon exposure to water.
Agricultural granules containing active ingredients also contain solid inert ingredients that may serve as a diluent and/or help maintain the granules in a stable, solid state. These solid inert ingredients may include, for example, clays, starches, silicas, sulphates, chlorides, lignosulfonates, carbohydrates such as dextrines, alkylated celluloses, xanthum gums and guaseed gums, and synthetic polymers such as polyvinyl alcohols, sodium polyacrylates, polyethylene oxides, polyvinylpyrrolidones and urea/formaldehyde polymers like PergoPak M® (registered trademark of Albemarle Corporation). The active ingredient(s) contained in a granule may be melted into a liquid, dissolved in a solvent or dispersed in a liquid, which may then be sprayed onto or absorbed into the solid inert ingredients. In the absence of effective solid inert ingredients, dry granules may be physically unstable and, in the case of solid particles, slowly breakdown forming a dust or powder or, in the case of granules containing liquid built-in adjuvants, slowly breakdown forming large liquid droplets as a result of Ostwald Ripening. Many solid inert ingredients used in agricultural granule formulations generally have good water solubility or dispersibility.
Adjuvants are important components of granules and are defined as substances which can increase the biological activity of the active ingredient, but are themselves not significantly biologically active. Adjuvants assist with the effectiveness of the active ingredient such as, for example, by improving the delivery and uptake of an herbicide into a target weed plant leading to improved biological control.
Adjuvants, in the form of solids or liquids, can be added directly to a formulated agricultural product, such as a granule, to provide improved performance of the product upon application. Commonly used adjuvants may include, for example, surfactants, spreaders, petroleum and plant derived oils and solvents and wetting agents. Examples of commonly used adjuvants include, but are not limited to, paraffin oil, horticultural spray oils (e.g., summer oil), methylated rape seed oil, methylated soybean oil, highly refined vegetable oil and the like, polyol fatty acid esters, polyethoxylated esters, ethoxylated alcohols, alkyl polysaccharides and blends, amine ethoxylates, sorbitan fatty acid ester ethoxylates, polyethylene glycol esters, organosilicone based surfactants, ethylene vinyl acetate terpolymers, ethoxylated alkyl aryl phosphate esters and the like. These and other adjuvants are described in the “Compendium of Herbicide Adjuvants, 9th Edition,” edited by Bryan Young, Dept. of Plant, Soil and Agricultural Systems, Southern Illinois University MC-4415, 1205 Lincoln Drive, Carbondale, Ill. 62901, which is available for viewing on the internet at http://www.herbicide-adjuvants.com/.
The term “built-in adjuvant” refers to one or more adjuvants that have been added to a particular formulation, such as a granule or liquid formulation, at the manufacturing stage of the product, rather than at the point of use of the product such as, for example, to a spray solution. The use of built-in adjuvants simplifies the use of agrochemical products for the end-user by reducing the number of ingredients that must be individually measured and applied.
Rice is an important cereal crop grown in many parts of the world and is cultivated under both wet and dry conditions. Control of weeds in rice is very important in order to maintain high levels of agricultural productivity. Use of herbicide granules for weed control in flooded rice paddies and fields is a very common agronomic practice in many rice growing regions. New herbicide granule products that offer improved performance relative to current products are needed.
Cyhalofop-butyl, (2R)-2-[4-(4-cyano-2-fluorophenoxy)phenoxy]propanoic acid butyl ester (CAS#122008-78-0), is a member of the aryloxyphenoxypropionic acid class of herbicides which are known in the art as the fop herbicides and is used to control grass weeds in rice. Cyhalofop-butyl is marketed as Clincher® herbicide (registered trademark of Dow AgroSciences LLC) and is sold in granule (GR), oil in water (EW) and emulsifiable concentrate (EC) formulations and exhibits good selectivity to rice when used in both dry land and flooded paddy applications.
Existing commercial granule formulations of cyhalofop-butyl contain relatively large amounts of solid inert ingredients such as potassium chloride, clay or starch combined with relatively small amounts of built-in adjuvants such as aromatic solvents. These built-in adjuvants consist of a maximum of from about 15 to about 20 per cent by weight relative to the total weight of the cyhalofop-butyl granule in currently marketed products. The limited built-in adjuvant content of current granule products can limit the biological performance of cyhalofop-butyl herbicide due to a minimal herbicidal adjuvant effect.
The present invention provides an improvement to existing solid herbicide compositions used to control weeds in rice by allowing higher loadings of built-in adjuvant and thereby offering improved herbicidal efficacy on weeds in flooded rice paddies or fields.